34461A DMM data logging with 34980A DAQ

Hello. I am measuring voltage drop on several DUTs at externally triggered intervals with my Keysight 34980a DAQ and 34922a Multiplexer Module. I want to add operating current measurements, but the Multiplexer Module doesn't support these measurements, so in comes the 34461a DMM to save the day. With a bit of creative signal routing, I have the DMM in series with all the DUTs to measure current (Power Supply [+] --> DMM --> Multiplexer Bank 2 COM [+] --> Bank 2 Channels 1036-1041 [+] (closed) --> DUTs 1-6 --> Power Supply [-] ) and the Vdrop being measured with the DAQ's internal DMM on Multiplexer Bank 1 Channels 1001-1006.

Using a few SCPI sequences in benchlink data logger pro (which controls the DAQ), I'm able to run the following sequence each time the DAQ is triggered:

-Close DAQ channels 1036-1041 (if not already closed) to power the DUTs

-Scan and measure Vdrop on DAQ channels 1001-1006 using internal DMM

-Setup the external DMM configuration (if not already configured)

-Open channels 1036-1041 and close one channel at a time to measure current with the external 34461A DMM. The sequence goes something like:

34980A DAQ: ROUTe:CLOSe:EXCLusive (@1036)

delay 250 [allows circuit to settle]

34922A DMM: INITiate:IMMediate

...and rinse and repeat for each channel on the scan list. The entire sequence takes about 2 seconds.

What I haven't been able to figure out is how to log the external 34461A DMM's data when controlled remotely. BenchLink doesn't support the 34461A DMM, and (more annoyingly) BenchVue doesn't support the 34980A DAQ. I can't send any queries (like FETCh?) with BenchLink. The test runs too long (~32 hours) to simply let the DMM run & record, and (as mentioned in other discussions) it does not generate time stamps in the CSV data (really!?). Actually, I can live without the time stamps in this case, as I only need a manageable 180 data points and have corresponding time stamps from the DAQ. However, I'm a little fuzzy on how to trigger the DMM directly from the DAQ, though I do have an Ext Trig/ VM Comp cable running between the two. I'm new to this setup and haven't yet had any luck with it.

If you've got any ideas on how to get the 34922A DMM to log data or otherwise incorporate it into my test setup, I'd love to hear them. Thank you for reading my novel.

Another way to do this is put a calibrated resistor across a 34922A channel, measure the voltage drop and calaulate I = V/R. The 34980A internal DMM is basically a 34410A DMM which is equivalent to the newer 34461A.

Yes. The import thing is to not break the current path. Insert the known value resistor in the DUT current path, then connect leads from both sides of the resistor to the Hi and Lo terminals of a 34922A multiplexer channel. Then you can scan across multiple resistors if you wish. It doesn't matter if you break the voltage path when you switch to another channel. That has no effect on the DUT or the measurements.